Issue #5829: modify LoaderTest.js for cc.async refactored.
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-js into Iss5829_JsDocs
Merge pull request #743 from dingpinglv/Iss5829_JsDocs

Issue #5829: modify LoaderTest.js for cc.async refactored.